Bisphenols produced from the condensation of phenols, particularly the bisphenol produced from the condensation of phenol per se and acetone enjoy a growing importance as chemical intermediates, particularly in the fields of epoxy resins and polycarbonate resins.
The most important bisphenol, 2,2-bis(4-hydroxyphenyl)propane (also called para, para-diphenylolpropane or Bisphenol A), is generally prepared by reacting phenol and acetone in the presence of an acidic catalyst such as hydrochloric acid along with a sulfur compound such as methyl mercapton as a co-catalyst. This method is disclosed in U.S. Pat. No. 2,730,552. However, the reaction between phenol and acetone to form 2,2-bis(4-hydroxyphenyl)-propane also forms a number of byproducts including 2-(2-hydroxyphenyl)-2-(4-hydroxyphenyl)propane, also called ortho, para-diphenylolpropane, which is an isomer of 2,2-bis(4-hydroxyphenyl)propane. Further impurities include 2,2-bis(2-hydroxyphenyl)propane, higher condensation products such as trisphenols (condensation products of three moles of phenol and two moles of acetone) and chroman derivatives (internal condensation products of two moles of phenol and two moles of acetone), plus still higher condensation products in the form of resins and tars. In addition, a major drawback to the use of mineral acid catalysts is that any acid present in the product must be neutralized or washed out before the product is recovered. All liquid catalyst systems will have the problem of removing the liquid catalyst from the product stream.
In order to combat some of these above-noted problems, various ion-exchange resins, either alone or in combination with a mobile co-catalyst such as mercapton, have been disclosed to catalyze the condensation reaction of a ketone with a phenol to produce bisphenols. Among the various processes are those disclosed in U.S. Pat. Nos. 3,049,568; 3,049,569; 3,153,001; 3,172,916; 3,221,061; 3,242,219; 3,242,220; 3,394,089; 3,496,239; 3,634,341; and 3,760,006.
A new solid ion exchange resin has been found that gives a much higher conversion at high selectivities than the previously known commercial catalysts.